Chapter 3 Flashcards
Cell
- Structural and functional unit of life
- Basic unit of life
- Organismal functions depend on individual and collective cell functions
- Biochemical activities
Cell Diversity
- Over 200 different types of human cells
- Types differ in size, shape, sub-cellular components, and functions
General Cell (All Cells)
- All cell have some common structures and functions
- Human cells have three basic parts:
- -Plasma membrane
- -Cytoplasm
- -Nucleus
Plasma Membrane
Flexible outer boundary
-lipid bilayer and proteins constantly changing fluid mosaic
-plays dynamic role in cellular activity
Separates intracellular fluid (ICF) from extracellular (ECF)
–Interstitial fluid (IF)= ECF that surrounds cells
Membrane Lipids
Lipid Bilayer
Phospholipids
- Phosphate heads: polar and hydrophillic (water liking)
- Fatty acid tails: nonpolar and hydrophobic (water fearing)
Membrane Proteins
-Allow communication with environment
-Most specialized membrane functions
2 Types
-Integral Proteins
-Peripheral Proteins
Integral Proteins
Firmly inserted into membrane
- Have both hydrophobic and hydrophilic
- Function as transport proteins (channels and carriers), enzymes, or receptors
Peripheral Proteins
- Loosely attached to integral proteins
- Include filaments on intracellular surface for membrane support
- Function as enzymes
6 Functions of Membrane Proteins
Look at Diagram Cards
- Transport
- Receptors for signal transduction
- Attachment to cytoskeleton and extracellular matrix
- Enzymatic Activity
- Intercellular Joining
- Cell-cell recognition
Glycocalyx
“sugar coverings” at cell surface
- lipids and proteins with attached carbohydrates (sugar groups)
- Every cell has different pattern of sugars
Cell Junctions
2 types
3 subtypes
Some are "free" EX- blood cells, sperm cells Some bond into communities 3 types: -Tight junctions -Desmosomes -Gap junctions
Tight Junctions
Adjacent integral proteins fuse form impermeable junction encircling cell
-prevents movement
Desmosomes
“Rivets” or “spot-welds” that anchor cells together at plaques (thickenings on plasma membrane)
- Linker proteins between cells connect plaques
- Lends stability to cell
- Reduces possibility of tearing
Gap Junctions
Transmembrane proteins form pores that allow small molecules to pass from cell to cell
-for spread of ions, simple sugars, and other small molecules between cardiac or smooth muscle cells
Plasma Membrane
Cells currounded by interstitial fluid (IF)
-contains thousands of substances; amino acids, sugars, fatty acids, vitamins, hormones, salts, waste products
Plasma membrane allows cell to:
-obtain what is needed from IF
-Keep out what it does not need
Membrane Transport
Plasma membranes selectively permeable -some molecules pass through easily; some do not Two ways substances cross membrane -Passive processes -Active processes
Passive Processes
- No cellular energy required
- Substance move down concentration gradient
- Diffusion (2)
- Osmosis
Diffusion
Molecules to move down or with their concentration gradient (speed of movement is determined by molecule size and temperature
Molecule will passively diffuse through membrane if:
-lipid soluble
-small enough to pass through membrane channels
-assisted by carrier molecule
3 Types of Diffusion
Look at Diagram Cards
- Simple Diffusion
- Carrier and Channel Mediated Facilitated Diffusion
- Osmosis
Simple Diffusion
Nonpolar lipid-soluble (hydrophobic) substances diffuse directly through phospholipid bilayer
EX. oxygen, carbon dioxide, fat-soluble vitamins
Carrier-Facilitated Diffusion
Certain lipophobic molecules transported passively by;
-binding to protein carriers
-moving through water-filled channels
Transmembrane integral proteins are carriers
Used when sugars are too large for channels
Channel-Facilitate Diffusion
Watery channels formed by transmembrane proteins
Selectively transport ions or water
Two types:
-Leakage (always open)
-Gateway (controlled by chemical or electrical signals)
Osmosis
Water moves through: -lipid bilayer -specific water channels Occurs when either water or solvent is too high on one side or the other than either: -through impermeable; osmosis occurs until equilibrium reached -through permeable; both solutes and water across membrane until equiilibrium reached
Pressures of Osmosis
Hydrostatic: back pressure of water on membrane
Osmotic: tendency of water to move into cell by osmosis
Importance of Osmosis
Look at Diagram Cards
Causes cells to swell and shrink
change in cell volume disrupts cell function, especially in neurons
Tonicity
Ability of solution to alter cell’s water volume
3 tonics- iso, hyer, hypo
Isotonic
Solution with same non-penetrating solute concentration as cytosol
Hypertonic
Solution with higher non-penetrating solute concentration than than cytosol
Hypotonic
Solution with lower non-penetrating solute concentration than cytocol
Active Processes
2 Types
Requires ATP to move solutes across a plasma membrane because:
-Solute too large for channels
-Solute not lipid soluble
-Solute not able to move down concentration
Two types
-Active Transport
-Vesicular Transport
Active Transport
Requires carrier proteins to move solutes against concentration gradient
Requires energy (ATP)
Energy stored in ionic gradients used indirectly to drive transport of other solutes
Most common is Sodium Potassium Pump
Sodium Potassium Pump
Look at Diagram Cards
Carrier (pump) called Na+-K+ ATPase, located in plasma membranes
Na+ and K+ channels allow slow leakage down concentration gradients
Na+-K+ pumps works as exchanger
-pumps against Na+ and K+
-high intracellular K+ concentration
-high extracellular Na+ concentration
Maintains electrochemical gradients for function of muscle and nerve tissues
Allows all cells to maintain fluid volume
